Continuous casting machine



Jan. 23, 1968 J. CARTON CONTINUOUS CASTING MACHINE 7 Sheets-Sheet 1Filed May 27, 1965 Jan. 23, 1968 CONTINUOUS CASTING MACHINE J. CARTON 7Sheets-Sheet 2 J. CARTON CONTINUOUS CASTING MACHINE Jan. 23, 1968 7Sheets-Sheet 5 Filed May 27, 1965 Jan. 23, 1968 Filed May 27, 1965 J.CARTON CONTINUOUS CASTING MACHINE 7 Sheets-Sheet 4 Jan.23,1968 J. CARTON3,364,979

CONTINUOUS CASTING MACHINE Filed May 27, 1965 7 Sheets-Sheet 5 Jan. 23,1968 J. CARTON 3,364,979

CONTINUOUS CASTING MACHINE Filed May 27, 1965 7 Sheets-Sheet '7 UnitedStates Patent 3,364,979 CONTINUOUS CASTING MACHINE Jean Carton, Paris,France, assignor to Compagnie Francaise Thomson-Houston, Paris, France,a corporation of France Filed May 27, 1965, Ser. No. 459,202 Claimspriority, application France, June 9, 1964, 977,539, Patent 1,434,123 14Claims. (Cl. 164154) ABSTRACT (3F THE DISCLGSURE A continuous coppercasting machine comprising a centerless annular ingot mold (2) having amassive head (24) with a casting groove (4) in its top and a longslender cooling flange (26) depending from the center of the head. Themold is supported with the lower end of its cooling flange restingfreely on a centerless annular support (28) mounted on rollers (52) anddriven in rotation through roller (60). Annular walls (38, 40)upstanding from support (28) define an annular trough in which a body ofcooling liquid is formed to a controlled depth in which the coolingflange (26) of the mold (2) is immersed. Molten copper is poured intothe casting from tundish (12) and solid copper rod is continuouslyextracted from the groove at (16) and directly passed to ahot-rollingmill (20), FIGURE 1.

This invention relates to the continuous casting of metals in the formof elongated elements or rods of indefinite length and uniform crosssection. The invention is more especially concerned with the continuouscasting of non-ferrous metals, particularly copper, into rods capable ofbeing directly hot-rolled and processed (e.g. drawn) into wire, stripand other metal products progressively as they solidify.

In conventional copper Wire-drawing plants in which wire is produced forthe electrical and related industries, the usual procedure is to startoperations with copper castings known as Wire-bars, which are thickoblong bars of rectangular cross section. Such wire-bars may he, say,about 1.3 meters long and may weigh from 60 to 140 kilograms. These arefirst heated to a temperature in the range of BOO-900 C. and hot-rolledinto rod stock of from 6 to 12 millimeters diameter. This may require upto twenty rolling passes or more. The hot-rolled rod, after cleaning andpickling, is passed to the wire-drawing machines where it is reduced toits desiredfinal diameter which may range anywhere from some millimetersto the order of one hundredth of a millimeter in size.

It would be extremely advantageous if the copper could be cast not asseparate bars, but instead in the form of a continuous rod capable ofbeing passed directly as it solidifies from the casting apparatus to theinitial processing stage such as hot-rolling mill. This would at astroke eliminate one or more reheating furnaces (as required to reheatthe wire-bars to hot-rolling temperature) and almost all of the largeand expensive rolling mills used at present in order to reduce thewire-bars to the dimensions at which they can be fed to the wire drawingmills. The saving in space, equipment, labour and energy would beimmense.

There have been many proposals in the prior art to provide continuouscasting equipment for non-ferrous metals which would make such type ofoperation feasible. Certain of these proposals have taken the form of alargeradius casting wheel, supported for rotation about its axis (e.g.vertical), and formed with an annular casting groove in its rim. As thewheel rotates, a stream of molten metal is continuously poured into thecasting groove at one point of its circular path, and the solidifiedmetal rod is continuously withdrawn from the groove at another point ofthe path.

Although the principle involved in such a continuous casting system issound, practical results have not come up to expectations, and theactual operation of such systems has been found too unrealiable andunsatisfactory for general industrial purposes, in spite of the veryimportant advantages pointed out above, which the use of such systemswould otherwise afiord.

The chief ditficulties encountered have concerned the thermal conditionsin the system. The molten copper is poured into the casting groove at atemperature of say 1150 -C. It must be completely solidified at itspoint of emergence from the groove, about three quarters of acircumference beyond the pouring point. However, it must not be allowedto solidify too far ahead of its point of emergence since otherwise itcould not be pulled out from its arcuate shape in the groove to astraight condition without cracking. The optimal temperature range atwhich the copper rod should be extracted in order to be passed directlyto a hot-rolling mill, is 800 C. surface temperature and not more than900 C. core temperature. The maintenance of these conditions requiresenergetic cooling as well as precise thermal control near the castinggroove and around the periphery of the casting wheel. At the same timeit is important that the thermal expansion-contraction eflects caused bythe sharp temperature gradients inherent in such an apparatus shall notset ilp damaging stresses in the annular mold, nor tend to distort thecasting groove and affect the uniformity of the cross section of thecontinuous cast rod.

The attainment of the results just enumerated comprise chief objects ofthis invention.

According to an important feature of the invention, the rim of thecasting wheel or annular ingot mold has a cross sectional shapewhichincludes a massive head portion with an upwardly-open castinggroove therein, and a relatively long and slender flange or cooling finof tapered shape depending from the head portion. Further, the annularmold is centreless, that is, free from any web, spokes, arms or the likeradially inward of the rim, so that said rim with the casting groovetherein is free to expand in an uninhibited manner circumferentially.This centreless annular mold is supported for rotation about an idealaxis which is generally vertical, and for this purpose said mold is madeto rest with the lower end of its depending cooling fin freely engagingunder gravity the flat top of an annular supporting member, which isdriven in rotation by suitable means such as rollers. For cooling themold, there are provided walls defining an annular trough on the top ofthe supporting member, containing a body of cooling liquid, generallywater, in which said cooling fin is immersed.

The annular supporting member preferably also is in the form of acentreless ring, e.g. of cast steel, and is supported and driven so asto be freely expansible relative to its stationary support structure,whereas the copper casting wheel is in turn freely expansible relativeto the annular cast-steel supporting member.

With such an arrangement it has been found possible to exercise highlyprecise control over the temperature of the metal in the casting grooveby simply varying the depth of the body of water in the trough in whichthe cooling flange or fin of the annular mold is immersed.

The annular mold is preferably made of copper for maximum conduction ofheat, and its slender tapered fin provides a path for the rapiddissipation of heat from the casting groove to the surrounding Water.

At the same time the relatively much more massive head, in which thecasting groove is formed, possesses easily and accurately the body ofcooling liquid in the trough. f The provision for free independentexpansion of the continuous casting retains a thermal inertia and thusstabilizes the temperature of the metal in the casting groove, resultingin a steady, continuous decrease in temperature around the circumferencefrom the point at which the moltenmetal is poured to the a point atwhich the solid rod is withdrawn. The final temperature of the metal atthis point of withdrawal can be adiusted as by varying the depth ofsteel or cast iron annular supporting member and the copper annular moldprevents darn-aging distortion to the parts of the casting machine andensures that the uniform undistorted cross section throughout.

Owing to the accurate temperature control achievable with the improvedcontinuous casting machine it becomes possible to feed the cast roddirectly as it solidifies and is stripped out of the casting groove, toa hot rolling mill thus eliminating an intermediate reheating step.

The various objects and novel features of the invention will becomeapparent from the ensuing description of an exemplary embodimentselected by way of illustration but not of limitation and with referenceto the accompanying drawings wherein:

FIG. 1 is a perspective view, somewhat simplified, of the main parts ofan improved continuous copper casting machine; 7

FIG. 2 is a larger-scale View in perspective and in section generally online 11-11 of FIG. 1 further showillustrated in FIG. 1;

ing certain additional parts not FIG. 3 is a cross sectional viewshowing in detail a preferred contour used for the annular casting mold;

FIG. 4 is a cross section, generally on the line IV-IV of FIG. 1, on anenlarged scale;

FIG. 5 is a small-scale schematic plan view of the machine and shows inphantom the positions assumed by the casting wheel and other parts atelevated casting temperature, the displacements from the full-linepositions being considerably exaggerated for clarity;

FIG. 6 is a large-scale perspective View of the extractor deviceassociated with the casting wheel;

FIG. 7 is a large-scale fragmentary view in cross section of. thecasting groove and casting therein and illustrates a heat-isolatingcoating lining the walls of the groove, in exaggerated form;

FIG. 8 is a partial view on a scale larger than that of FIG. 1, showingthe casting wheel and its supporting means in cross section and theladle and feeder tank in elevation together with the movable mountingmeans for the feeder tank.

The continuous copper casting machine illustrated includes as anessential component a revolving annular ingot mold or casting wheel 2supported for rotation in the direction indicated by the arrow A in FIG.1 in a generally horizontal plane, through means later described. Aswill be apparent from the large-scale cross sectional views of FIGS. 2,3, 4, 6, 8, the annular mold 2 is formed in its upper surface with anannular casting groove 4.

Near the annular mold 2 there is positioned a conventional casting ladle6 containing a body of molten metal, in this instance copper, suppliedthereto at a suitable casting temperature from an appropriate meltingfurnace not shown. The ladle '6 is supported on a frame generallydesignated 8 by way of the horizontally aligned pivots 10 for rotationabout a horizontal rocking axis, whereby the molten contents of ladle 6can be poured into a regulating feeder tank or tundish 12 which is supported from frame 8 in a position such that a bottom outlet orifice oftundish -12 directly overlies at all times a point of the casting groove4 in the annular mold 2. The supporting means for tundish or feeder tank12 will be later described in detail. The molten metal can thus 4,. bemade to flow as a regular uniform-rate stream the casting groove 4, andas the casting wheel 2 revolves, a charge of molten metal isthuscontinuously deposited into the casting groove. 1

The metal thus deposited into the casting groove 4 rather rapidly coolsand solidifies as it is carried around- .with the revolving mold 2, sothat at a point situated some three fourths of a circumference or sobeyond the point at which the stream of molten metal is poured, themetal has solidified. At or shortly beyond the point of solidification,the continuous solid copper rod is stripped from the casting groove t bymeans of an extractor device generally designated 16 and later describedin detail. Essentially this extractor device consists of a stationaryramp or wedging member inserted into the groove 4 so as to lift thesolidified metal rod out of the groove.

The continuous rod 18 thus extracted is shown as being fed directly tothe rolls of a conventional hot rolling mill 2i). i

The reference 22 designates a sprayer device, schematically shown,positioned to overlie the groove 4 in the are I thereof beyond theextracting station 16 and ahead of the casting station 14; and servingto spray a suitable lubricant composition into the empty casting grooveas later described in greater detail. I 1 a a The annular ingot mold 2is formed with a cross sectional contour clearly shown in FIG. 3 asincluding a relatively massive upper head part 24 in which thecastinggroove 4 is formed, and a relatively thin, downwardly taperedcircumferential flange 26 extending downward from the head 24. y

A supporting and cooling assembly for the annular mold 2 is shown ascomprising an annular support member 28 which may be a steel or ironcasting and has the general cross sectional shape of an invertedchannel. Secured to the fiat upper surface of the member 28 are a seriesof supporting blocks or shims 30 which extend radially across theannular upper surface of member 28 and are spaced. circumferentially.around that surface. The blocks 30 have flat upper surfaces over a majorintermediate portion of their extent, and tap er down at their ends asshown at 32. The annular mold 2 is supported on the shims 30 atop themember 28 under its own weight, with the lower end surface of flange 26resting upon the flat upper surfaces of the shims 30 substantiallycentrally thereof. To prevent appreciable circumferential displacementsof the mold 2 relative to the supporting member 28, one or more radiallyextending key elements such as the one shown at 34' in FIG. 2 aresecured to the upper surface of member 28 in'addition to the shims 30,and project upwardly into a complementary notch 36 formed in the lowerend part of the flange 26 of the the upper surface'of member 28. At thesame time, the

ingot mold 2 remains at all times connected for bodily rotation with itssupporting member 28 as the latter is driven in rotation through meansto he later described.

An annular trough for a cooling liquid is defined atop the supportingmember 28 and around the flange 26 of the ingot mold by a pair ofannular walls 38 and 40 made of steel strip, 'aifixed to the verticalsides of the supporting member 28 and projecting upwardly thereabove.The trough thus defined contains a body of cooling liquid, such as watersubstantially free from mineral salts capable of depositing as scaleover the side surfaces of flange 26 and interferring with heat transfer.Means are provided for maintaining the level of cooling water 46 in thetrough at a constant, adjustable height, and include a feed pipe 42 anda discharge pipe 44 supported at stationary posiinto 5 tions throughmeans not shown and having their ends bent as shown to projectdownwardly into opposite sides of the trough. The feed pipe 42 may beconnected to a constant-delivery pump, not shown, and discharge pipe 44may be similarly connected to a pump, not shown, which will operatewhenever the level of the water 45 reaches up to the end orifice of thepipe 44. Means including a sealed mechanism casing 47 and handwheel 49are provided for adjusting the vertical position of discharge pipe 44thereby to maintain the level of the liquid at a correspondin position.It will be understood that any suitable means other than those justdescribed may be provided for maintaining the level of the coolingliquid 46 in the trough at an adjustable elevation. It will be notedthat the water delivered by the feed pipe 42 rapidly fills the bottom ofthe trough on both sides of the cooling flange 26 of the ingot moldowing to the gaps provided beneath said flange between thecircumferentially spaced supporting shims 30 and that the response toany readjustment of the water level is very rapid especially owing tothe fact that the trough is revolving whereas the pipes 42, 44 arestationary. Moreover, owing to the extremely effective heat transferpresent between the flange 26 of the ingot mold and the surroundingwater, the degree of control thus obtained over the temperature in theingot mold 2 is etficient, sensitive, and precise. Thus in one specificprocess later described in detail, a change of one centimeter in the heiht of the water level 46 in the trough was found to produce a consistentvariation of about 50 C. in the temperature of the metal in the ingotmold.

Desirably, the water level 46 in the trough may be automaticallyregulated to maintain the output temperature of the casting at aprescribed value. For this purpose there is schematically indicated inFIG. 1 a temperature sensing member 51 such as a thermocouple contactinga side of the rod 18 as it issues from the casting groove beyondextractor 16. The output conductors. 53 of temperature senser 51 providethe electrical signal input to a conventional SEI'VO-IllOiOI unit 55which may include an amplifier and reversible motor operating thehandwheel 49 through a. drive connection schematically indicated at 57so as to raise or lowe the outlet pipe 44. Thus when the electric signalfrom temperature senser 51 present on conductors 53 indicates anincrease in the temperature of the casting above a prescribed upperlimit servomotor 55 will act to raise outlet pipe and thus increase thedepth of the body of cooling Water in the trough, while in case of adrop in the sensed temperature below a prescribed lower limit the motor55 will act to lower pipe 44.

It will he observed that while the shims 30 constitute a convenientmeans of providing the necessary liquid passages over the surface of thebottom of the trough across the flange 25 to ensure the establishment ofthe requisite hydrostatic balance in the body of liquid on both sides ofsaid flange, other means may be used for this purpose, such as byproviding circumferentilaly spaced cutouts in the lower edge of theflange 26.

It is frequently desirable to cause the casting and solidification ofthe cast metal to proceed under controlled atmosphere conditions, suchas in an inert or reducing gas, or water vapor. For this purpose, anannular hood 48 of inverted channel shape in crosssection, is suspendedfrom stationary overhead structure 49 as by means of the suspensionrings t} and hooks or other means. The sides of the annularchannel-shaped hood 48 project downward into the body of water 46 in thecooling trough thereby defining a gastight annular tunnel surroundingthe ingot mold 2 and the metal cast in the casting groove 4. It will beunderstood that the stationary hood 48 may be provided with suitableapertures, not shown, for the pouring of the stream of molten metal fromtank 12 into the groove and for the withdrawal of the solid continuousrod 18. In operation the cooling water 46 heated by the flange 26 of theingot mold generates considerable amounts of steam which displace theair from the interior of the hood 48 and inexpensively provide adesirable nonoxidizing atmosphere for casting copper and other metals.If desired however, means may be connected with the hood 48 forcirculating some other desired atmosphere through it, such as an inertgas. In yet other cases, the hood 48 may be removed entirely and thewhole process carried out in free atmosphere.

The means for rotatably supporting the assembly including the annularmold 2 and its supporting and cooling means, will now be described. Therotatable supporting means are shown as including three pairs of rollers52 angularly equispaced around the circumference of the annularstructure as shown in FIGS. 1, 4 and 5. Each pair of rollers 52comprises two aligned, frustoconical rollers 52a and 52b freelyrotatable on a common generally horizontal shaft 54 and having theirperipheral surfaces defining a common conical surface. The two rollers52:: and 52b of each pair are engaged by the lower end surfaces of theouter and inner walls 28a and 28b respectively, of the channel-shapedsupporting member 28. It will be noted that said walls 28a and 28b arebevelcut to unequal lengths so as to conform to the common conicalsurface defined by the rollers 52:: and 521).

With each pair of rollers 52 there is associated a roller 56 freelyrotatable on a vertical shaft 58 and engaging the outer vertical surfaceof the radially inner wall 28b of the member 23. The horizontal shaft 54and the vertical shaft 58 of each of the three sets of three supportingrollers described may be supported from a common fixed frame structureof suitable character, not shown. It will be noted that the arrangementdescribed provides for the rotational support of the entire annularstructure about an ideal axis of revolution without having tomaterialize such axis physically as a shaft. The steel annular supportmember 28 is thu allowed to expand circumferentially with temperature,and in so doing its flanges 28a and 28b will shift radially over therollers 52a and 52b. The rollers being separately rotatable about theircommon shaft 54, the contact thereof with the respective flanges 23a and23b is substantially slip-free.

The supporting structure (not shown) for the shafts 54 and 58 of thethree sets of supporting and centering rollers 52 and 56 may be soarranged that the entire annular assembly is supported in asubstantially horizontal plane for rotation about a vertical axis.However, if desired said supporting structure may be so arranged thatsaid annular assembly is supported in a general plane tilted to thehorizontal, in a direction away from the casting station at which themolten metal stream pours into the casting groove 4 of ingot mold 2,thereby opposing any tendency to backflow of the molten metal as itenters the groove 4 with a tangential component in the direction ofarrow A as earlier described. It is found in some cases that if themetal is allowed to flow back and upstream from its point of injectionalong the groove 4, as may tend to occur in the absence of theaforementioned tilt imparted to the annular ingot-mold 2 and itssupporting assembly, the uniformity of the cross sectional dimensions ofthe cast metal bar is disturbed. The said general tilt successfullyeliminates this defect and may thereby improve the quality of the finalproduct. A preferred range for the angle of tilt with respect to thehorizontal plane is found to be from about 10 to about 20.

cans are provided for imparting rotation to the annular assemblycomprising support 28 and the ingot mold 2 resting upon it. As shown inthe drawings the cylindrical vertical surface of the radially inner wall28b of the annular member 28 is engaged by a friction roller 60 securedon the vertically projecting shaft of a suitable motor 64 mounted on thefixed frame structure. Directly opposite to the point of engagement ofradially inner wall 28b by drive roller 60, the outer surface of theradially outer wall 28a of annular member 28 is engaged by a backingroller 66. Roller 66 is mounted for free rotation by a compressionspring 74 thereby urging the backing roller 66 into resilient pressureengagement with the wall 28a and urging wall 28b against drive roller60. The backing pressure exerted by roller 66 is made adjustable throughdisplacement of a movable abutment member, not shown, abutting the rearend of spring 74 and preferably comprising a screw and nut devicesupported from the frame member 72.

The drive arrangement thus described is simple and efficient, and at thesame time permits free circumferential or radial expansion of theannular supporting member 28 with temperature, owing to the virtuallypoint character of the areas of engagement between said member and therespective drive and backing rollers 60, 66. Thus, at high temperaturesthe steel annular member 28 expands radially to assume the form shown(in an exaggerated manner) in- FIG. in broken lines, in which theradially inner surface of member 28 no longer vengages the centeringrollers 56 but still rides freely on the supporting rollers 52 asearlier explained.

The extractor device generally designated 16 in FIG. 1 will now bedescribed in greater detail with reference to FIG. 6. As known per seand as indicated earlier herein,

the extractor device 16 includes a wedge-shaped member 7 6 of suchtransverse dimension as to be freely insertable into the bottom of thecasting groove 4, and having an upper surface tapering down into thedirection of movement of the ingot mold 2 indicated by arrow A. Thelarger end of the wedge member 76 is pivoted on a transverse horizontalshaft 78. The shaft 78 is mounted on suitable supporting structure, notshown, which is gennerally stationary but permits sufficient freedom ofmotion for said shaft 78 to allow the lifter member 76 to remainproperly positioned within the groove 4 regardless of thermal expansionand contraction of the annular ingot mold 2.

It is also noted that the feeder tank or tundish 12 while being mountedin a generally stationary manner from the frame 8 as earlier indicated,is arranged to be capable of freely following the displacements of thecasting groove 4 as the ingot mold 2 expands and contracts with changesin temperature.

For this purpose, as illustrated in FIG. 8, the feeder tank or tundish12 is secured on a truck 80 movable on a bracket 82 secured to a side ofthe ladle structure 6 and projecting above the casting wheel 2. Thetruck is provided with rollers 84 riding on rails 86 attached to thehorizontal top of the bracket 82 in a direction radial to the castingwheel. A pivot shaft 88 projecting vertically downward from the truck 80has a follower roller 90 pivoted to its lower end so as tobe engageablewith the cylindrical inner surface of the casting wheel 2. The followerroller 90 is biassed into engagement with the casting wheel 2 by meanshere shown as a compression spring 92 having its ends engaging suitableseating surfaces on the bracket 82 and truck 80*. Instead of a spring acounterweight may be used as the biassing means. The arrangement is suchthat when follower roller 90 is engaging the rim of the annular castingmember 2 as shown, the pouring outlet 94 of the feeder tank ispositioned substantially centrally of the casting groove 4. It will beevident that with this arrangement, the stream of molten metal will beproperly delivered into the casting groove regardless of any distortionsof the casting member 2 and its supporting member 28 due to temperaturevariations.

Important features of this invention relate tothe construction of theingot mold 2 and to the cross sectional contour imparted to it, andthese features will now be described in detail with especial referenceto FIG. 3. As earlier indicated, the upper rim or head part of the crosssection of the ingot mold is relatively massive. This is necessary inorder to impart the desired dimensional and thermal stability to thecasting groove 4 therein and to the ingot mold as a whole. Desirably,said rim or head part 24 is approximately octagonal in outer contour(disregarding the groove 4). In contrast to the massive rim or head part24, the flange 26 must be relatively long and slender in order toachieve the desired rapid rate.

of heat transfer between the ingot mold 2 and the surrounding coolingwater medium. It will be noted that the rim 24 is heated by directcontact with the hot metal in groove 4 whereas flange 26 is cooledthrough contact with the cooling water. This results in alarge degree ofdifferential expansion therebetween with changes in temperature, themassive head part 24 expanding to a greater degree than the flange 26.To allow for this,

differential expansion and prevent damaging strains being set up and theoccurrence of dimensional distortion in the casting groove and hence inthe cast product, the

cross sectional contour of the annular ingot mold 2 is conically angledto the general axis of symmetry of the annular mold, in adownward-outward sense. That is,

considering in FIG. 3 the axis of symmetry AA'of the v general crosssectional outline of the annular ingotmold 2 as above defined, this axisAA is tilted downwardly away from the central axis of revolution of theannular mold, indicated at OO. In yet other words, the surface ofrevolution generated by the symmetry axis AA of the cross sectionaloutline about the symmetry axis 00 of the entire ingot mold isna conewhose apex lies above the general plane of the ingot mold. In thismanner it will be understood that'when the ingot mold as a whole isheated to its average overall working temperature, the increased radialand circumferential expansion of the hot massive upper part 24 over thatof the cool flange 26, causes the annular ingot mold member 210 distortin such a way that its cross sectional contour is bodily rotated in asense (clockwise in FIG. 3) that tends to bring the symmetry axis AA ofsaid contour into parallelism with the symmetry axis 00 of the annularingot mold member 2.

It can be shown that the proper value to be imparted to the cone angleformed between the two above-defined axes AA and O0 in the coldcondition of the ingot mold is given approximately by the relation 2hE Tin radians) (1) where R is the mean radius of the annular ingot' moldmember, it its total height or depth dimension, 0: is the linear thermalexpansion coefficient of the mold. material, and AT is the differencebetween the mean temperatures in the rim or head 24 and flange 26 duringa casting process. Obviously the correct value to be selectedfor dependson the overall size and cross sectional dimensions of the ingot mold,the material from whichit is made and the temperature conditions appliedduring trated in FIG. 3 the bottom wall of the casting groove 4 isslanted downward in a radially inward direction i.e.

towards the centre axis 00 of the annular mold, relative to the crosssectional contour of the mold as defined above. The slant angle, whichis relatively small, is indicated as 0 in FIG. 3. In other words,considering now the symmetry axis BB of the casting groove 4 as distinctfrom the symmetry axis AA of the outer cross sectional contour of theingot mold previously considered, then said axis BB (which is normal tothe bottom surface 100 of the groove), forms an angle 9 with respect tothe axis AA, this angle being directed in the same sense as is the angle:1: formed by axis AA withrespect to axis 00.

Consequently it will be clear that the axis BB forms an angle (+0) tothe general axis of symmetry of the annular mold. The reason for thusslanting the bottom of the casting groove is, essentially, to providecompensation for centrifugal force.

That is, the molten metal initially poured into the casting groove at 14is highly fluid, and the centrifugal force created by the rotation ofthe mold about its centre axis 00 therefore causes the free uppersurface of the metal in the groove 4 to slant upwardly in the radiallyoutward direction, away from centre axis 00. Should the molten metal beallowed to solidify in this configuration without special precautions,the resulting casting would have an asymmetrical cross sectional contourin which the top and bottom surfaces would not be parallel. By slantingthe bottom surface of the casting groove 4 as indicated, this efiect ofcentrifugal force can be compensated and a substantially trulysymmetrical casting can be obtained.

It can be shown that the proper value to be imparted to the slant angle0 between the two above-defined axes BB and AA is given approximately bythe relation 0=Rw /g (0 in radians) (2) where R, as before, representsthe mean radius of the annular mold, w is the angular velocity of therevolving mold in radians per second, and g is the acceleration ofgravity. For most practical conditions a suitable angular range for theangle 0 is approximately from 1 to 3". For the specific case of thepractical example to be disclosed herein, the value of 6 is about 140.

The casting groove 4 has substantially straight side surfaces 102 whichdiverge slightly in the upward direction symmetrically to the oppositesides of the groove symmetry axis BB, in order to facilitate withdrawalof the solidified casting from the groove. This angle of divergence ortaper may be of the order of 2 on each side, as here indicated. Thesides 102 of the casting groove connect with the bottom 100 of it by wayof rounded corners, as shown, the radius at each corner being preferablyabout 2 mm. This radius is substantially the same as the radius assumeddue to surface tension at the lines of contact of the upper free surfaceof the molten metal with the sides 102 of the casting groove. As aresult there is produced a casting in which the cross sectional contouris a trapezoid having equally rounded corners.

Prior to the casting operations, the inner surfaces of the castinggroove 4 are coated with a thin layer of a suitable heat-insulating andrefractory substance, such as any of various silicates, aluminates orbentonite. This coating has the dual function of preventing overheatingof the mold and over-cooling of the metal, and the coating thickness isdetermined by test to obtain optimum temperature conditions in thecasting at the point of its extraction from the casting groove. In thecase of the copper castings here considered, these optimum conditionsare such that the cast rod as it is withdrawn at the extraction station16 is fully solidified to the core, and is still at a surfacetemperature not substantially less than about 800 C. (a suitable rangeof temperatures throughout the cross section of the trapezoidal rod isfrom 800 to 900 C). In these conditions the continuous rod as it issuesfrom the ingot mold can be directly passed through the hot-rolling mill20 without having to be reheated, with considerable advantage to theoverall economy of the process.

A generally suitable range of thicknesses for the heatinsulating liningjust mentioned is from 0.1 to 0.5 millimeter. It has been found howeverthat for best results the thickness of this lining, as indicated at 104in FIG. 7, is preferably not uniform, but is somewhat greater in theupper or outer parts of the groove sides 102 and then 7 tapers down to auniform value along the bottom surface of the groove. This precautionserves to oppose a tendency to a premature cooling of the metal as itfirst contacts the side walls 102 and consequent defects such as cracksin the casting. Alternatively, a similar result can be obtained byimparting to the groove sidewalls an incurvated contour somewhat asindicated in dotted lines at 102 in FIG. 7. In this figure, reference106 indicates the cast metal in the groove 4.

Over the heat isolating coating 104 just described, there is provided athin film of lubricant such as colloidal graphite, serving to preventadhesion of the solidified metal to the underlying surface. Thislubricant coating is applied continuously during the casting process, asalready indicated, by means of the sprayer unit 22. in the castinggroove 4 in the empty arcuate segment thereof between the extractorstation 16 and the pouring station 14. The rate of delivery of thesprayer 22 is adjusted to coat the inner surfaces of the groove 4 with athin film which may be of the order of a few hundredths of onemillimeter in depth.

In a specific embodiment of the invention now to be described in detailby way of example, the annular ingot mold 2 had a mean radius R=l,400mm. as measured from the centre axis 00 to the centre of the castinggroove 4. The vertical dimension of the mold was h= mm. The crosssectional shape of the mold was substantially as shown in FIG. 3, thegroove 4 being about 22 mm. deep and formed and dimensioned to provide afinished rod having a trapezoidal cross section 13.5 mm. in altitude and13.5 mm. average width. The conical angle in the cold condition of themold was 2, and the slant angle 9 of the groove bottom 100 to thesymmetry axis AA of the cross section was 140. The head portion 24 was55 mm. thick and the flange 26 tapered down from 30 mm. to 10 mm. over alength of 70 mm.

The annular mold 2 was rotated from motor 64 through drive roller 60 ata uniform angular rate of 4.32 r.p.m., or w=0.452 rad/ sec. The linearvelocity V of withdrawal of the continuous cast rod was therefore V=Rwor :38 meters/minute, and the casting output was about 3.7 metric tonsper hour.

The cooling system described was operated to maintain a body of waterbetween 30 and 70 mm. deep in the annular trough surrounding the coolingflange 26. Under these conditions it was found that the metal in thecasting groove 4 cooled at a rate such that the rod emerging atextractor station 16 had just solidified to the core but its surfacetemperature was still somewhat above 800 C. The rod was seen to possessa highly regular trapezoidal cross section, with its top and bottomsurfaces substantially parallel. The cross section was strictly uniformthroughout the length of the rod, about 600 meters for a one-ton coppermelt. The crystal structure of the casting was excellent, fine-grainedand free from oxidation, occlusions, cracks, blow-holes and otherdefects.

As this rod emerged continuously from the extracting station 16 at atemperature in the range of 800 to 900 C., it was immediately fedthrough the hot rolling mill 20 in which it was converted to a round rodor wire 10 mm. in diameter. This was then fed continuously to theconventional wire-drawing mills in which it was drawn to variousstandard gauges.

During test runs, measurements were taken with thermocouple probes todetermine the temperatures in various parts of the annular mold. It wasfound that the mean temperature within the massive head portion 24 ofthe cross section was T C. and that in the cooling flange 26 was T =6 2C. Thus the temperature differential AT=88 C. Substituting this valueinto Equation 1 given above, and further putting R=l.4, h=0.l2 and e=l.7l0 (the linear expansion coefiicient for copper), there is found =0.035radian, or 2, the selected value indicated above. Measurements showedthat during the casting process the flange 26 effectively assumed underthe differential expansion effect earlier explained a substantiallyupright position parallel to the centre axis 00 of the annular mold.

the desired overall compensation both for differential expansion and forcentrifugal effects as earlier explained. Inadequate control overthermal conditions in prior-art continuous casting machines of'the classto which the invention relates has been responsible for many and seriousdifficulties which have heretofore prevented continuous castingprocesses from gaining wide acceptance in the field of non-ferrousmetallurgy, particularly though not exclusively copper wire-drawingplants. These difficulties have included temperature instability. Thatis, it was not found practicable to cool the annular mold with theefficiency and uniformity required to create and maintain a steady,continuously decreasing temperature gradient around the circumference ofthe mold all the way from the molten metal pouring station to theextracting station, as would be essential if the temperature of thecasting at its point of extraction was to be accurately maintainedwithin its critical range. This range (800- 900 C; for copper) iscritical for several reasons as earlier indicated. The cast rod musthave solidified to the core before it can be extracted, yet it must nothave solidified too far ahead of its point of extraction since in suchcase it would set in a curved state owing to the curvature of theannular mold, and it would then tend to crack as it is straightened outby extractor 16. Also, the rod should preferably be at a temperaturewhere it can be directly hot-rolled without reheating.

In the invention, the requisite temperature stability and consequentprecise control over the temperature of the casting at its point ofextraction is achieved mainly through the feature that the crosssectional shape of the annular mold includes two sections differingradically in their geometric and physical characteristics: a relativelymassive head or rim portion having the casting groove formed in it, anda slender cooling fin integrally depending from the head and immersed acontrollable depth in cooling water. The cooling fin assures efiicientdissipation of heat from the casting groove to the cooling medium at acontrollable rate, while the massive head owing to its large moment ofinertia imparts thermal as well as dimensional stability to the castinggroove and the molten metal therein. The thermal inertia of the headsection surrounding the casting groove ensures that the temperature inthe casting groove will at no time tend to change abruptly but willpresent a steady, continuously decreasing gradient all the way from thepouring station to the extracting station, so that the final temperatureof the casting at the extracting station remains always perfectly welldetermined and fully controllable.

Another class of difiiculties present in conventional continuous castingsystems of the type specified has resided in the occurrence ofdeformations both in theparts of the casting machine itself and in thecasting, as a result of differential expansion effects. Thesedifficulties have been eliminated in the invention through theconstruction of the revolving annular mold as a generally horizontal,centreless annulus capable of free and uninhibited circumferentialexpansion without distorting the cross section of the casting groove.Furthermore, since the centreless annular mold of the invention ispreferably made of copper for optimal conduction of heat through itscooling 'fin as explained in the foregoing paragraph, it is contemplatedthat the mold is supported and driven by resting under its own weightupon an annular supporting member of cast steel, with provision for freeexpansion of the copper mold and steel supporting annulus independentlyof one another, thereby preserving the feature of free circumferentialexpansibility of the copper mold, and with further provision for drivingthe supporting annulus 12 and mold in bodily rotation withoutinterfering with the free expansibility. of either annular part.

Various modifications may be made in the specific embodiment describedand shown without departing from the scope of the invention. The crosssectional shape of the annular mold may be altered, especially asregards the cross section of the casting groove therein, whilepreserving the main geometric characteristics.

Various ancillary devices of generally conventional character may beassociated with the casting machine.

Thus suitable guiding means and draft tension-control arrangements maybe interposed between the extracting station 16 and the hot-rollingstand 20, and may serve-to impart a controllable retarding force to therod 18. as it issues from the extractor.

Servo-mechanism of conventional type may be provided for automaticallycontrolling the rateat which molten metal is poured from the feedertank'12, and/ or the rate of rotation of the casting wheel 2 from drivemotor 64, in order to regulate the vertical dimension of the continuouscast rod. Such servo-mechanism may be tied in with the servo meansearlier described herein for controlling the depth of cooling water inthe trough.

What I claim is: I

1. A continuous metal casting machine comprising:

an annular casting member in the form of a circumferential-lycontinuously integral centreless rim positioned in a generallyhorizontal plane and havinga cross-sectional contour including a massivehead POI".

tion with an upwardly-open casting groove therein and a cooling finportion depending from the head portion; said cooling fin portioncomprising a relatively long and slender flange of a material havinghigh heat conductivity extending front a substantially central area ofthe undersurface of said head portion; means mounting the casting memberfor centreless rotation about a generally vertical ideal central axis,of rotation, said mounting means comprising a supporting member having agenerally flattop and means driving said supporting member in rotationabout said generally vertical axis, the casting member resting upon, thesupporting member with the lower end of said flange of the dependingcooling fin freely engaging said flat top so as to be driven in rotationcircumferentially with the supporting member while being freely movableradially with respect thereto under forces of differential thermalexpansion and contraction; means for retaining a body of cooling liquidatop the supporting member in which said cooling fin portion of thecasting member is immersed with both outer sides of said flange beingcontacted by the liquid; and

means for pouring molten metal into the casting groove at one point ofits rotational path and means forextracting a continuous casting fromthe groove at another point of its path.

2. A continuous casting machine comprising:

an annular casting member in the form of a centreless rim positioned ina generally horizontal plane and having a cross-sectional contourincluding a massive head portion with an upwardly open casting groovetherein and a relatively long and slender cooling flange portiondepending therefrom;

an annular trough means disposed coaxially with and under said castingmember with the lower end of said 13 means for pouring molten metal intothe casting groove at one point of its rotational path and means forextracting a continuous casting from the groove at another point of itspath; whereby said massive head portion with molten metal in the groovethereof will undergo in operation considerably greater thermal expansionthan said slender cooling flange immersed in the cooling liquid and thecasting member will consequently be distorted so that said head portionthereof is rotated radially outward relative to the cooling flangeportion; and said casting member being formed so that the crosssectionalcontour thereof at ordinary temperature has an axis of symmetry inclinedto said axis of rotation in a downward-outward direction an angularamount such as to cancel said distortion and render said cross sectionalcontour substantially vertical under casting temperature conditions. 3.A casting machine as defined in claim 2, wherein said casting groove hasa generally flat bottom wall slanting at a small angle downward in theradially inward direction relative to said cross sectional contour.

4. A casting machine as defined in claim 3, wherein the casting groovehas a generally trapezoidal cross sectional contour with side wallsdiverging upward from perpendicnlars to said bottom wall.

5. A continuous casting machine comprising: an annular casting member inthe form of a circumferentially continuously integral centreless rimhaving a massive head portion with an upwardly-open annular castinggroove formed in the top thereof and a relatively long and slenderannular cooling flange depending from a substantially central area ofsaid massive head portion at least said flange being made of a materialhaving high heat conductivity;

annular trough means disposed coaxially with and under the castingmember with the lower end of the cooling flange resting on a bottomsurface of the trough; means for delivering cooling liquid into thetrough at one point and withdrawing liquid from the trough at anotherpoint, including means for varying the depth of the body of liquid inthe trough, said liquid contacting both outer side surfaces of saidcooling flange;

means for bodily rotating the trough means and casting member about agenerally vertical ideal central axis of rotation;

means for pouring molten metal into the casting groove at one point ofits rotational path and means for extracting a continuous casting fromthe groove at another point of its path;

means for sensing the temperature of the casting adjacent said lastpoint; and

servo-means connected with the temperature sensing means and connectedwith the depth varying means to increase the depth of cooling liquidwhen the sensed temperature rises and decrease said depth when thesensed temperature decreases.

6. A continuous casting machine comprising:

an annular casting member in the form of a circumferentiallycontinuously integral centreless rim having an annular upwardly-opencasting groove in the top thereof and a cooling flange portion dependingfrom a substantially central area of said massive head portion at leastsaid flange being made of a material having high heat conductivity;

annular trough means underlying the casting member generally coaxiallytherewith with the lower end of the flange portion resting on a bottomof the trough means;

means for bodily rotating the trough means and casting member about agenerally vertical ideal central axis of rotation;

generally stationary inlet pipe means positioned to deliver coolingliquid into the trough at at least one point of its rotational path,said liquid contacting both outer side surfaces of said cooling flange;

generally stationary outlet pipe means positioned to withdraw liquidfrom the trough at at least one point of said path; and

means for pouring molten metal into the casting groove at one point ofits rotational path and means for extracting a continuous casting fromthe groove at another point of its path.

7. A casting machine as defined in claim 6, wherein said outlet pipemeans is arranged to have an end thereof dipping into the trough fromthe top thereof, an extractor =pump connected with another end thereof,and means for vertically displacing said outlet pipe means for varyingthe level of cooling liquid in the trough means.

8. A continuous casting machine comprising:

an annular casting member in the form of a circumferentiallycontinuously integral centreless rim having a massive head portion withan annular upwardlyopen casting groove in the top thereof and an annularcooling flange depending from a substantially central area of saidmassive head portion at least said flange being made of a materialhaving high heat conductivity;

means mounting the casting member for centreless rotation about agenerally vertical ideal central axis of rotation, said mounting meanscomprising an annular supporting member having a generally flat top uponwhich the lower end of the cooling flange rests freely under gravitywhereby the casting member is circumferentially rotatable with thesupporting member while being freely movable radially thereof underforces of differential thermal expansionand contraction;

a driving roller engaging one peripheral side surface of the annularsupporting member and a backing roller engaging an opposite peripheralside surface of the supporting member in radial alignment with thedriving roller and motor means for rotating the dirving roller to rotatethe supporting and casting members about said axis while permitting freecircumferential expansion of the supporting member;

means defining an annular trough atop the supporting member forcontaining a body of cooling liquid in which said cooling flange isimmersed with both outer side surfaces thereof contacted by the liquid;

means for pouring molten liquid into the casting groove at one point ofits rotational path and means for extracting a continuous casting fromthe groove at another point of its path.

9. A casting machine as defined in claim 8, wherein the supportingmember has an undersurface which is frustoconical with respect to saidaxis of rotation, and a plurality of circumferentially spaced supportingidler rollers engaged by said undersurface and having their axesgenerally radial with respect to said axis of rotation.

19. A casting machine as defined in claim 8, including a plurality ofcirc-umferentially spaced positioning idler rollers engaging an innerone of said peripheral side surfaces of the annular supporting memberwhen said member is under ordinary temperature conditions.

11. A continuous casting machine comprising:

an annular casting member in the form of a circumferentiallycontinuously integral centreless rim having a massive head portion withan annular upwardlyopen casting groove in the top thereof and an annularcooling flange depending from a substantially central area of saidmassive head portion at least said flange being made of a materialhaving high heat conductivity;

annular trough means underlying the casting member generally coaXiallytherewith with the lower end of the flange freely resting under gravityon a bottom surface of the trough;

means defining flow passages over said bottom surface between theopposite sides of said flange to allow free establishment of hydrostaticbalance across the flange in a body of cooling liquid present in thetrough said liquid contacting both outer side surfaces of said flange;

means for delivering cooling liquid into the trough at one point andwithdrawing liquid from the trough at another point for providing saidbody of liquid in the trough;

means for rotating the trough means and thereby rotating the castingmember while enabling free relative expansion of the casting member withrespect to the trough means;

means for pouring molten metal into the casting groove 1 at one point ofits rotational path and means for withdrawing a continuous casting fromthe groove at another point of the path;

and means for varying the hydrostatic level of the body of liquid in thetrough so as to maintain a prescribed temperature in said casting as itissues from the casting groove.

12. A machine as defined in claim 11 wherein said metal is copper andsaid groove has substantially uniform cross-sectional dimensions.

erally horizontal plane is tilted from the true. horizontal plane at arelatively small downward angle away from said metal pouring means inthe direction of rotation of the casting member.

14. A machine as defined in claim 8, wherein said casting member is madeof copper and said supporting member is made of steel.

References Cited UNITED STATES PATENTS 7 359,348 3/1887 Daniels 164-268368,817 8/1887 Daniels 164278 405,914 6/1889 Schutlz 164-276 2,659,94911/1953 Properzi .164278 3,284,859 11/1966 Conlon etal 164 -2591,902,559 3/1933 Kemp 164 348 I FOREIGN PATENTS 125,883 6/1928Switzerland. 528,359 7/1956 Canada.

J. SPENCER OVERHOLSER, Primal) Examiner.

R. D. BALDWIN, Assistant Examiner.

13. A machine as defined in claim 1, wherein said gen- 25

